Guide and support structure

ABSTRACT

The invention relates to a guide and support structure ( 1 ) that in addition to providing a secure and stable guide support for the plug-in unit and good electric contact properties enhances the removal of heat from the plug-in unit. This is achieved by means of a guide and support structure having an upper web forming a guide channel for a plug-in unit and being connected to a base of the structure through side walls of the structure. The base is at least partially open in order to allow air flow through the interior of the elongated profile. By virtue of such a configuration blockage of a cooling-air flow will be significantly reduced. Such a reduced blockage of cooling-air flow will in turn enhance the cooling of plug-in units and will require less powerful fans for producing the cooling-air flow.

TECHNICAL FIELD

[0001] The present invention relates generally to a structure forsupporting electronic component carriers, such as printed circuit cards,in a chassis, such as an enclosure.

BACKGROUND

[0002] It has been common practice for many years to mount printedcircuit boards or cards in enclosures as so called plug-in units thatmay be easily inserted into and/or removed from the enclosure forreplacement or repair. Conventionally, the plug-in units are slidablyreceived in guide and support structures that are commonly named boardguides or board rails. The main purpose of the board guide is tosecurely guide the plug-in unit into position in the enclosure, so thatit may be connected to the backplane of the enclosure. In its simplestform, the conventional board guide typically consists of a molded guidechannel manufactured from a non-conductive material and havingintegrally formed attachment means.

[0003] However, for most applications board guides are presentlyrequired to establish electrical contact between a conductive pattern orlayer on the printed circuit board or card and a wall of a conductiveenclosure. Such electrical contact or connection may be required bothfor the purpose of employing the enclosure as ground for the operationof the separate circuit boards and/or electronic components carriedthereon and for the purpose of eliminating or at least minimizingelectromechanical radiation emanating from the boards or cards.

[0004] Several attempts have been made to develop board guide structuresthat will meet the requirements for establishing an electricalconnection between the circuit boards and the enclosure. Typically, suchfurther developed board guides have a composite structure consisting ofa solid channel member accommodating a separate contact and/or guidemember. The solid channel member is normally molded or extruded from asynthetic resin material and accommodates a contact and/or guide memberhaving several board contact spring fingers formed of a conductivemetal. The contact and/or guide member is also provided with integralenclosure contact means extending through openings in the channel memberto contact the enclosure. In other arrangements the channel member isformed of a thermally conductive material, such as aluminum, in order topromote heat transfer from the circuit board.

[0005] Examples of such prior art composite board guides are disclosedin U.S. Pat. Nos. 5,187,648, 5, 805,429 and 5,533,631.

[0006] U.S. Pat. No. 4,007,403 discloses a board guide that is formed asan integral unit of for instance stainless steel. Accordingly, thisboard guide eliminates some of the above discussed disadvantages. On theother hand, it comprises very few board contact points, which means thata reliable electrical contact with an inserted circuit board cannot beguaranteed.

[0007] In the board guides of the above discussed general designs it isdifficult to provide a reliable electrical contact between the board andthe enclosure and to maintain such contact during the useful life of theboard guide. For the composite design, the reason for this is mainly theseparate channel members and contact members. Specifically, the channelmember is typically attached to the enclosure and the enclosure contactmeans of the guide and/or contact member are clamped between the channelmember and the enclosure by said attachment. This means that cold flowor aging of the channel member material will directly affect theelectrical connection that is basically also rather unreliable due tothe fact that the contact is established only at the individual contactpoints of the board contact fingers and of the enclosure contact means.In this regard, the board guide design disclosed in U.S. Pat. No.4,007,403 is even more unreliable. Here, the electrical contact betweenthe board and the enclosure is restricted to the attachment means at thetwo ends of the structure, leaving the entire middle area of thestructure free of any positive attachment to a supporting enclosure.

[0008] For the same reason the heat transfer capacity of theconventional board guide designs is quite limited, especially where thechannel member consists of a resin material. In such board guides, thetransfer of heat from the circuit board is restricted mainly to thelimited contact points of the guide and/or contact member. Even in theabove mentioned structures where the channel member is formed as anextruded aluminum profile or as an integral unit of stainless steel, thetransfer of heat from the board to the channel member is restricted bythe limited contact points. In the composite design heat transfer isalso restricted even further by the often casual transfer from the guideand/or contact member to the channel member.

[0009] Furthermore, the conventional board guides cause additionalproblems in applications involving air-cooled enclosures. In suchapplications, cooling air flows through perforations in the enclosurewalls to remove heat from the mounted circuit boards. In the abovediscussed conventional board guides a considerable portion of the flowof cooling air is effectively blocked by the guide structures having arigid base forming or supporting the channel or channel member,respectively. The composite structure with the solid channel member aswell as the integral guide structure of U.S. Pat. No. 4,007,403, arealso both comparatively wide, so that they cover and thus block arelatively large number of perforations. In view thereof, the use ofsuch board guide designs necessitates the use of more powerful fans toproduce the required cooling-air flow through the walls of theenclosure.

SUMMARY

[0010] The invention overcomes the above problems in an efficient andsatisfactory manner.

[0011] A general object of the invention is to provide a solution to theproblem of providing an effective guide and support structure for aplug-in unit that is intended for slidable insertion into a chassis.

[0012] In particular, it is an object of the invention to provide animproved guide and support structure that enhances the removal of heatfrom an inserted plug-in unit, in addition to maintaining a secure andstable guide and support for the plug-in unit and good electric contactproperties.

[0013] Briefly, this is achieved by means of a guide and supportstructure having an upper web forming a guide channel for a plug-inunit. Through side walls of the structure, the upper web is connected toa base of the structure. With such a configuration the guide and supportstructure will be slim and will basically not cause any unnecessaryblockage of a cooling-air flow in a supporting chassis. Moreover, thebase is at least partially open in order to allow air flow through theinterior of the structure. Such a partly open design of the base willadditionally reduce blockage of the cooling-air flow. This reduction ofthe blockage of cooling-air flow will in turn enhance the cooling of theplug-in units and will require less powerful fans for producing thecooling-air flow.

[0014] In an embodiment of the invention, the guide and supportstructure is formed as an integral unit from an electrically as well asthermally conductive metallic plate material. The metallic platematerial will not only provide the appropriate support and guide for theplug-in unit, but will also secure good electrical contact throughoutthe useful life of the structure.

[0015] In another embodiment of the invention, the base of the guide andsupport structure has means for fixing the structure against the chassisas well as means for establishing electrical contact with the chassis.With such a configuration, good electric contact will be establishedboth with regard to the chassis and to the plug-in unit.

[0016] In another embodiment of the invention the guide and supportstructure is configured as an elongated profile having a base formingmeans for conducting heat from a plug-in unit to the chassis. By virtueof the metallic material, the guide and support structure will also actas an effective heat sink.

[0017] In a practical embodiment the base of the guide and supportstructure is formed by free edges of the side walls, said free edgesserving to support the structure against a chassis wall and to fix thestructure to said wall as well as to provide the desired electrical andheat conducting contact therewith. Leaving the entire space between theside wall edges open will provide maximum cooling-air flow into theinterior of the profile.

[0018] In a further embodiment of the invention the pressure drop of thecooling air flow caused by the guide and support structures of a chassisis reduced even further by providing apertures in at least one of theside walls of the elongated profile, said apertures serving to form apath for the cooling-air flow from the interior of the elongated profileto the interior of the chassis.

[0019] In other embodiments of the invention the guide and supportstructure is designed to provide a particularly secure guiding of theplug-in unit into position and a particularly firm support of saidplug-in unit in a fixed position, and to provide a particularlyeffective electrical contact between the plug-in unit and the guide andsupport structure.

[0020] In further embodiments of the invention, the guide and supportstructure is designed to provide possibilities for a rationalmanufacturing of the integral guide and support structure, and toprovide a secure attachment of the entire guide and support structure toa chassis wall.

[0021] These and further objects of the invention are met by theinvention as defined in the appended patent claims.

[0022] In summary, the present invention provides the followingadvantages over the state of the art:

[0023] A good electrical contact will be maintained at all times;thereby

[0024] Securing a reliable grounding of the plug-in unit; and

[0025] An effective shield against electromagnetic radiation;

[0026] The guide and support structure will secure an effectiveconduction of heat from the plug-in unit, acting as a heat sink;

[0027] The guide and support structure causes minimum blockage of acooling air flow, thereby further enhancing cooling of the plug-in unit;

[0028] The plug-in unit will be securely guided and supported in thestructure;

[0029] The support unit is extremely easy to handle and to mount,consisting of only one unitary piece.

[0030] Other advantages offered by the present invention will be readilyappreciated upon reading the below detailed description of embodimentsof the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The invention, together with further objects and advantagesthereof, may best be understood by making reference to the followingdescription taken together with the accompanying drawings, in which:

[0032]FIG. 1 is a top perspective view of a first embodiment of a guideand support structure according to the invention;

[0033]FIG. 2A is a partial perspective view of guide and supportstructures according to FIG. 1 attached to a schematically illustratedchassis and guiding and supporting schematically illustrated plug-inunits;

[0034]FIG. 2B is an enlarged view of a detail of the chassis illustratedin FIG. 2A, illustrating a slightly modified assembly of the guide andsupport structures;

[0035]FIG. 3 is a bottom plan view of the guide and support structure asillustrated in FIG. 1;

[0036]FIG. 4A is a cross section through the guide and support structureillustrated in FIGS. 1 and 3, taken along the line A-A of FIG. 3;

[0037]FIG. 4B is a cross section corresponding to that of FIG. 4A,illustrating the attachment of the guide and support structure to achassis wall and also schematically illustrating a carrier inserted intothe guide channel of the guide and support structure;

[0038]FIG. 5A is a partial bottom perspective view from one side of thefirst embodiment of the guide and support structure;

[0039]FIG. 5B is a partial bottom perspective view from the oppositeside of the first embodiment of the guide and support structure;

[0040]FIG. 6 is a cross section through a second embodiment of the guideand support structure according to the invention, taken along line B-Bof FIG. 8;

[0041]FIG. 7 is a partial bottom perspective view of the secondembodiment of the guide and support structure illustrated in FIG. 6;

[0042]FIG. 8 is a bottom plan view of the second embodiment of the guideand support structure that is illustrated in FIGS. 6 and 7;

[0043]FIG. 9 is a cross section through a third embodiment of the guideand support structure according to the invention, taken along line C-Cof FIG. 11;

[0044]FIG. 10 is a partial bottom perspective view of the thirdembodiment of the guide and support structure illustrated in FIG. 9; and

[0045]FIG. 11 is a bottom plan view of the third embodiment of the guideand support structure that is illustrated in FIGS. 9 and 10.

DETAILED DESCRIPTION OF EMBODIMENTS

[0046] The invention will be described below with reference to thedrawing figures that illustrate embodiments thereof adapted for use insupporting plug-in type PCB boards in a rack or sub-rack, such as in atelecommunications cabinet or magazine. However, it shall be understoodthat the invention is not restricted to this exemplifying embodiment orto such an application. The basic principles of the invention maylikewise be applied in association with guide and support structures forother carriers of electronic components and of the plug-in type.

[0047] Such alternative applications will cover any electronic componentcarrier of the plug-in unit type, such as printed circuit cards andelectronic modules, supported in an enclosure that may be referred to asa chassis, a cage or a rack and that accommodates an optional number ofsuch carriers. Therefore, modifications and variations of the inventionthat may be required in such applications fall within the scope of theinvention.

[0048] A first embodiment of the invention will now be described withspecific reference to drawing FIGS. 1-5. FIGS. 1, 3, 4A-B and 5A-Billustrate a presently preferred embodiment of the inventive guide andsupport structure 1 for plug-in cards or boards, whereas FIGS. 2A and 2Billustrate the inventive guide and support structure in a typicalapplication for supporting plug-in units 2 in a sub-rack 20.

[0049] According to the invention, the guide and support structure 1, orboard guide, is formed as a generally U-shaped (see FIGS. 4A and 4B)elongated profile that is manufactured as an intgral unit from ametallic plate material having good electrical as well as thermalconductivity. A presently preferred material is a tin-plated stainlesssteel grade, but other metal plate materials having the appropriateproperties may likewise be employed.

[0050] The elongated profile 1 consists of two spaced but substantiallyparallel first and second profile side walls 7, 8 respectively that areinterconnected at one end by an upper web portion 9, where “upper”refers to its positioning, in the attached condition, with regard to thewall 21 or 22 of the sub-rack or chassis 20. The opposite or lower endsor free edges 7A, 8A of the side walls 7, 8 form a base portion 5 of theguide and support structure 1 (se especially FIGS. 5A and 5B). The baseportion is completely open between the free edges 7A, 8A and is intendedto be supported against a side wall 21 or 22 of the sub-rack 20 in theattached condition.

[0051] A guide channel 3 is formed in the upper web portion 9 of theprofile 1, said guide channel likewise having a general U-shape, butbeing directed with its open side facing away from the base portion 5 ofthe profile 1. The guide channel 3 serves the main purpose of securelyguiding a plug-in unit 2 during insertion and of supporting the insertedunit 2 in a fixed position. In order to facilitate the initial insertionof a plug-in unit, an insertion ramp 3A is provided at the entrance tothe guide channel 3, said ramp having an inclined surface and outwardlydiverging side walls. In fact, an insertion ramp 3A is provided at eachend of the guide channel 3, so that a plug-in unit 2 may be insertedfrom either end thereof. This adds to the flexibility of the guide andsupport structure, since it may be attached to a chassis in two invertedpositions. Furthermore, the appropriate guide and support for a plug-inunit in the guide channel 3 is achieved by providing a continuos rigidbottom wall 3B and likewise rigid first and second channel side walls 3Cand 3D, respectively. Said channel side walls 3C, 3D are continues, thatis uninterrupted, over at least an essential portion of their height(see especially FIGS. 4A, 5A and 5B). The second channel side wall 3Dhas a larger uninterrupted height than the first channel side wall 3C,for reasons that will be explained further below.

[0052] A series of individual contact members 4 are formed in the firstprofile side wall 7, evenly distributed along the length of the profile.To be precise, the individual contact members 4 consist of a baseportion 4A and a contact portion 4B. The base portion 4A is formedbasically from the plate material of said first profile side wall 7. Thecontact portion 4B is formed basically from the material of the webportion 9, which results in the above mentioned reduced uninterruptedheight of the corresponding first channel side wall 3C. The contactportion 4B has a tapered and slightly rounded outer free end to allowinsertion of a plug-in unit, as will be discussed below. In theillustrated embodiment, the base portion 4A of the contact members 4 isprovided with a central first side wall aperture 11 serving as acooling-air exit, as will likewise be discussed further below. Thismeans that each base portion 4A actually consists of two spaced supportlegs 4A together supporting a contact portion 4B. Each support leg 4A isbent inwardly towards the guide channel 3 at a position 4C adjacenttheir connections to the remaining first profile side wall 7. Therebythe contact portion 4B is positioned at the proper position above theopen side of the guide channel 3 (FIGS. 4A and 4B), that is extendinginto the path of movement of an inserted plug-in unit.

[0053] Second side wall apertures 12 are provided in the second profileside wall 8 and partly in the upper web 9, likewise serving as the laterdiscussed cooling-air exits. The second side wall apertures 12 that areformed in the second profile side wall 8 are wider in the longitudinaldirection of the profile I than the first side wall apertures 11 formedin the first profile side wall 7. On the other hand, the first side wallapertures 11 extend further down towards the base portion 5. In essence,the cooling-air exit area provided by the second side wall apertures 12approximately equals the combined cooling-air exit area provided by thefirst side wall apertures 11 and the open area surrounding the contactmembers 4.

[0054] At the base portion 5 of the profile 1, each one of the freeedges 7A, 8A of the side walls 7, 8 is provided with a number of lockingtabs 6 that are formed integral with the side walls and that protrudedownwardly therefrom, as seen in the illustrations of FIGS. 4A and 4B.In the illustrated embodiment he locking tabs 6 are evenly distributedalong each free edge 7A, 8A, with the locking tabs of one edge 7 beingdisplaced with half a pitch along said edge in relation to the lockingtabs of the other edge 8. Such an arrangement is presently regarded asproviding the best distribution for obtaining a secure attachment to asub-rack wall. However, other arrangements for the locking tabs 6 mayprovide an equally secure attachment and the invention shall thereforenot be restricted to such a specific positioning of the locking tabs. Inany specific practical application the arrangement of the locking tabsshall be adapted to the pattern of the perforations of the chassis wall,to ensure that in the correct position of the structure 1 all of thetabs 6 will fit properly into a corresponding perforation 23.

[0055] With specific reference to drawing FIGS. 4A-B and 5A-B, it willbe seen that each locking tab 6 comprises a generally V-shaped main body6A. A first portion of the main body extends downwardly from the loweredge of an associated side wall 7, 8 of the profile 1, substantially inthe plane of said associated side wall. A second portion of the mainbody 6A is bent outwardly and then back towards the associated sidewall, forming an acute angle with the first portion. A support lug 6B isformed at the free end of the second portion by bending said free end tolie substantially in a plane that is transversal to the plane of theassociated side wall and that crosses said side wall at its lower freeedge. In the mounted condition said support lug 6B is intended to engagean inner surface of a wall 21 or 22 of a chassis 20. Furthermore, pawls6C are provided at each side of the first portion of the main body. Saidpawls are intended to engage an outer surface of said wall 21 or 22 ofthe chassis 20 to thereby fix the guide and support structure 1 to saidchassis wall.

[0056] It will be appreciated that with the above described design theinventive guide and support structure 1 may be manufactured in one piecein a very rational manner. In an initial step, the entire profile may bepunched from a metallic plate material in one single punching operation.Specifically, the free edges 7A, 8A of the side walls 7, 8, the lockingtabs 6, the individual contact members 4, the insertion ramps 3A and thefirst and second side apertures 11 and 12 may be formed in such aninitial step. In subsequent bending operations, the U-shaped guidechannel 3 is formed; the entire elongated profile 1 is given its generalU-shape; and the insertion ramps 3A, the contact members 4 and thelocking tabs are given their final shape.

[0057]FIG. 2A illustrates the use of the inventive guide and supportstructure 1 in a typical air-cooled chassis or sub-rack 20 that isschematically illustrated by means of two walls 21, 22 thereof. Thewalls 21, 22 are provided with evenly distributed perforations 23 thatserve the double purpose of allowing cooling-air to enter the interiorof the rack 20 to cool plug-in units 2 inserted therein and ofmaintaining an appropriate shield against electromagnetic radiation. Thecooling-air flow is typically created by means of fans that are providedoutside the sub-rack. This manner of providing a flow of cooling-air isconventional and will not be discussed in any detail, nor illustratedany further herein.

[0058] With reference to FIG. 2A, pairs of guide and support structures1 are provided at the same level in the two walls 21 and 22, that is inthe corresponding rows of the perforations 23. FIG. 2A illustrates theguide and support structures 1 that are attached to the wall 21 beingpositioned to the right in said drawing figure. It should be understoodthough, that guide and support structures 1 are attached in the samemanner to the inner side of the wall 22 being positioned to the left inthe drawing figure. Said further guide and support structures 1 are onlyvaguely visible in FIG. 2A, represented by the locking tabs 6 extendingthrough the chassis 20 wall 22.

[0059] In order to attach the guide and support structures I to thechassis 20 walls 21, 22, the locking tabs 6 are introduced into theappropriate perforations 23 of the walls 21, 22. Specifically, thelocking tabs are inserted with the point of the V-shape first, until thesupport lugs 6B engage the inner surface of the associated wall 21 or 22and the pawls 6C have been extended through the perforations 23 so as tobe in a position for engaging the outer surface of the wall. In thisway, the chassis wall 21 will be clamped between the pawls 6C on the onehand and the support lugs 6B and the free edges 7A, 8A of the side walls7, 8 on the other hand, as is clearly illustrated in FIGS. 3 and 4B. Thedistance W between the outer extremities of the two pawls 6C of eachlocking tab 6 slightly exceeds the diameter D of the perforations 23(see FIG. 3). This means that the side walls and/or the locking tabs ofthe guide and support structure 1 shall be elastically deformed wheninserting the locking tabs 6 into the perforations. Specifically, thisis done to position the pawls 6C approximately at the diameter of theassociated perforation, where they may be freely inserted. When thelocking tabs 6 have been fully inserted, the side walls and/or lockingtabs are released to allow them to spring back and to position the pawlsin a position where they both engage the outer surface of the chassiswall and positively lock the guide and support structure 1 to thechassis wall. In order to automatize the attachment of the guide andsupport structures 1 the necessary force for providing the elasticdeformation of the side walls and/or locking tabs is preferably appliedby means of a special tool that is not part of the invention and that isnot specifically disclosed herein.

[0060] Plug-in boards 2, normally having board fronts 2A, are theninserted into the chassis 20 by being slidably introduced into the guidechannels 3 of the appropriate pairs of guide and support structures 1.The initial insertion is facilitated by the provision of the insertionramps 3A. The further insertion of the plug-in boards 2 will be in adirection transversal to the individual contact members 4 that extendinto the path of the plug-in board. Through the tapered and slightlyrounded outer free end of the contact members 3, the insertion of theplug-in boards 2 will cause the contact members to be elasticallydeflected from said path of movement. With a plug-in board 2 fullyinserted into a guide and support structure 1, all of the individualcontact members 4 will therefore assist in biasing the board 2 againstthe second higher channel side wall 3D. A reliable electrical as well asthermal contact will be established between the board 2 and thecombination of the plurality of individual contact members ands therigid second channel side wall 3D having the larger uninterrupted heightand therefore having a larger contact surface. The large surface area ofthe second channel side wall in combination with the continuos bottomchannel wall 3B will also secure that the board 2 is properly guided andpositioned in the guide and support structure 1.

[0061] Furthermore, the described configuration of the guide and supportstructure 1 provides for an effective and secure electrical as well asthermal contact between the base 5 of the profile 1 and the chassis 20walls 21, 22. Specifically, the combination of the entire free ends 7A,8A of the side walls 7, 8 and the locking tabs 6 form a large effectivecontact surface. It will be appreciated that a very effective groundingof the plug-in board 2 will be achieved in this manner, through thecombination of the large continues contact surfaces and the reliableattachment of the structure to the chassis wall by means of the lockingtabs being formed integral with the contact means. It will likewise beappreciated that by manufacturing the entire guide and support structure1 as an integral unit from a thermally conductive material the structure1 will serve as an effective heat sink, especially so in combinationwith the discussed large contact surfaces relative to the plug-in unitas well as relative to the chassis walls.

[0062] In applications where the guide and support units 1 are employedin air-cooled sub-racks or chassis 20, it is desirable that the chassiswalls are as open as possible to allow the appropriate cooling-air flow.In such cases, cooling of the plug-in units will be further improved bythe extremely slim design of the structure 1. Specifically, the slimdesign blocks fewer per-forations than the conventionally designed boardguides, thereby permitting a larger un-interrupted flow of cooling-airthrough the chassis walls. This slim design is made possible by thedescribed configuration of the structure 1 being manufactured as anintegral unit from a metallic plate material.

[0063] The cooling-air flow is enhanced even further with the design ofthe described first embodiment having a base portion 5 being totallyopen between the free edges 7A, 8A of the side walls 7, 8. This openbottom aperture is indicated with the reference number 10 in FIG. 4A.With reference specifically to FIG. 4B, this means that cooling-air CAwill enter the interior of the profile 1 through perforations 23 thatwould conventionally be blocked by the board guide structure. From theinterior of the profile 1 this cooling-air CA will exit the profilethrough the first and second side wall apertures 11, 12, therebyassisting in removing heat from the mounted plug-in units 2.Experimental tests have been performed with an air-cooled sub-rack beingfully equipped with plug-in units. Said tests have indicated that byemploying guide and support structures 1 of the inventive design thepressure drop across the rack walls will be reduced to approximately 40%of the pressure drop resulting from the use of conventional boardguides. This in turn means that the cooling-air flow through the rackwill be increased by 10-30%, or alternatively that less powerful andtherefore less expensive fans may be employed for a given application.

[0064] Drawing FIGS. 6-11 illustrate modified second and thirdembodiments of the inventive guide and support structure 100 and 200respectively. Said embodiments are particularly suitable forapplications that require a large contact surface between the structureand a chassis wall in order to promote electrical contact and/orconduction of heat. The second embodiment is illustrated in FIGS. 6-8and mainly differs from the first embodiment by the provision of abottom wall 105 forming the base of the structure 100. The bottom wall105 extends between lower portions 107A, 108A of the side walls of theelongated profile 100. Specifically, in the illustrated embodiment theelongated profile 100 is likewise designed so that it may be punched outin one piece from a plate blank. Thus, the bottom wall 105 is formedintegral with the first side wall 107 and is bent inwardly from thelower portion 107A thereof, towards the lower portion 108A of the secondside wall 108.

[0065] In the illustrated embodiment the bottom wall 105 is continuosexcept for bottom apertures 110A that will be the result of forming thelocking tabs 106 provided at the lower end 107A of the first side wall107. Said locking tabs 106, with their main body 106A, support lug 106Band pawls 106C, are formed from the material of the bottom wall 105,whereas the locking tabs at the lower end 108A of the second side wall108 are formed in the same manner as by the first embodiment.Furthermore the first and second side wall apertures of the firstembodiment have been omitted, with the result that the second side wall108 is connected to the web 109 and the guide channel 103 along theentire length of the profile 100, without any interruption. Also, thebase 104A of the contact members 104 extends the full width of thecontact member and is continuously connected to the contact portion104B. Except for the described differences the structure 100 of thesecond embodiment is identical to that of the first embodiment and neednot be described any further. However, it shall be emphasized that inapplications requiring also an enhanced cooling-air flow, the guide andsupport structure 100 of the second embodiment may likewise be providedwith side wall apertures like those of the first embodiment as well aswith one or more additional bottom wall apertures 110B (indicated withdash-dot lines in FIG. 8).

[0066] Drawing FIGS. 9-11 illustrate a third embodiment of the guide andsupport structure 200. In this embodiment, the upper portion of theelongated profile 200 is identical to that of the first embodiment,whereas a bottom wall 205 like in the second embodiment forms the base205 of the profile. The main difference is that in the third embodimentthe locking tabs are formed as gripping hooks 206 that are punched outfrom the bottom wall 205, leaving bottom apertures 210A. Whereappropriate said bottom apertures might be supplemented by furtherbottom wall apertures 210B, as is outlined in FIG. 11. The grippinghooks 206 are formed approximately centrally in the bottom wall 205,with regard to the lower portions 207A, 208A of the side walls 207, 208,and are bent backwards toward the bottom wall 205 so as to be extendedin the longitudinal direction of the profile 200. With this design, thestructure 200 may be easily attached by positioning the free end of thehooks 206 in a perforation 23 and by then simply pushing the structure200 forward in the direction of the hooks. Each hook 206 will then beextended through the associated perforation 23 to grip the chassis wallfrom the outside.

[0067] Throughout the drawing figures, identical or corresponding partsof the guide and support structures of the different embodiments aregiven the same basic reference numeral, but with the addition of 100 inthe second embodiment and 200 in the third embodiment.

[0068] In further modified, but not specifically illustrated embodimentsof the invention any of the illustrated guide and support structures mayalternatively be provided with only one side wall aperture formed ineither one of the walls of the profile. Such a design may be appropriatefor specific applications requiring less than maximum cooling-air flow.

[0069] It will be understood by those skilled in the art that variousmodifications and changes may be made to the present invention withoutdeparture from the scope thereof, which is defined by the appendedclaims.

1. Guide and support structure (1; 100; 200) forming a guide channel (3;103; 203) for slidably receiving an edge of a plug-in unit (2), such asa printed circuit card or electronic module, and having a base portion(5; 105; 205) with means for supporting the structure against a chassis(20), mutually spaced but generally parallel side walls (7, 8: 107, 108;207, 208) extending outwardly from the base portion and resilientcontact members (4; 104; 204) extending into the path of movement of aplug-in unit being inserted into the guide channel for making electricalcontact with the plug-in unit, characterized by an upper web portion (9;109; 209) connecting outward ends of the side walls, in that the guidechannel (3; 103; 203) is formed in the upper web portion and in that thebase portion (5; 105; 205) is provided with at least one bottom aperture(10; 110A, 110B; 210A, 210B) forming a path with minimum blockage forcooling air (CA) flow from outside the chassis (20), through perforatedwalls (21, 22) of the chassis and into the interior of the structure (1;100; 200).
 2. Guide and support structure (1; 100; 200) according toclaim 1, characterized in that the web portion (9; 109; 209), the sidewalls (7, 8: 107, 108; 207, 208) and the base portion (5; 105; 205) withthe means (5; 105; 205) for supporting the structure is one integralunit formed of a metallic plate material having good electrical as wellas thermal conductivity.
 3. Guide and support structure (1; 100; 200)according to claims 1 or 2, characterized in that the base portion (5;105; 205) comprises means (6; 106; 206) for fixing the structure to thechassis (20) as well as means (5, 6; 105, 106; 205, 206) forestablishing electrical contact with said chassis.
 4. Guide and supportstructure (1; 100; 200) according to claims 2 or 3, characterized inthat the integral unit has the general form of an elongate plate profileand in that said base portion (5; 105; 205) forms means for conductingheat from an inserted plug-in unit (2) to said chassis (20).
 5. Guideand support structure (1) according to any of claims 1-4, characterizedin that the base portion (5) is formed by free edges (7A, 8A) of theside walls (7, 8), said free edges being spaced from the upper webportion and forming said means (5) for supporting the structure as wellas means for establishing electrical contact with said chassis and meansfor conducting heat from an inserted plug-in unit (2) to said chassis(20).
 6. Guide and support structure (1) according to claim 5,characterized in that the base (5) of the elongate profile is completelyopen between the free edges (7A, 8A) of the side walls (7, 8).
 7. Guideand support structure (1; 200) according to any of claims 1-6,characterized in that at least one of the side walls (7, 8; 207, 208),of the elongate profile is provided with side apertures (11, 12; 211,212) forming a path for cooling air (CA) from the interior of thestructure through said side wall (-s) and to the interior of the chassis(20).
 8. Guide and support structure (1; 200) according to claim 7,characterized in that side apertures (11, 12; 211, 212) forming a pathfor cooling air (CA) are provided in both side walls (7, 8; 207, 208),surrounding the guide channel (3; 203).
 9. Guide and support structure(1; 100; 200) according to any of claims 1-8, characterized in that theguide channel (3; 103; 203) that is formed in the upper web portion (9;109; 209) has a general U-shape with the open side of the guide channelfacing away from the base portion (5; 105; 205) of the elongate plateprofile, in that the guide channel has a continuos bottom wall (3B;103B; 203B) and continuous spaced channel walls (3C, 3D; 103C, 103D;203C, 203D) and in that individual resilient contact members (4; 104;204) extend from one of the side walls (7, 8: 107, 108; 207, 208) of theelongate profile into the path of movement of an inserted plug-in unit(2).
 10. Guide and support structure (1; 100; 200) according to claim 9,characterized in that the individual resilient contact members (4; 104;204) are formed partly from the plate material of one of the side walls(7,8: 107, 108; 207, 208) and partly from the plate material of theupper web portion (9; 109; 209).
 11. Guide and support structure (1)according to claims 9 or 10, characterized in that the side apertures(11; 211) in one of the side walls (7; 207) of the elongate profile areformed through a base portion (4A) of each individual contact member (4;204).
 12. Guide and support structure (100; 200) according to any ofclaims 1-5 and 7-10, characterized in that the base portion (105; 205)is formed by a bottom wall extending between lower edge portions (107A,108A; 207A, 208A) of the side walls (107, 108; 207, 208), said bottomwall (105; 205) forming the means for supporting the structure as wellas the means for establishing electrical contact with said chassis andmeans for conducting heat from an inserted plug-in unit (2) to saidchassis (20).
 13. Guide and support structure (1; 100; 200) according toany of claims claim 1-12, characterized by locking tabs (6; 106; 206)protruding from the base portion (5; 105; 205), the locking tabs beingadapted for insertion into perforations (23) in a wall (21, 22) of thechassis (20) and forming said means for fixing the guide and supportstructure to the chassis as well as means for establishing electricalcontact with said chassis and means for conducting heat from an insertedplug-in unit (2) to said chassis (20).
 14. Guide and support structure(1; 100) according to claim 13, characterized in that the locking tabs(6; 106) have a general V-shape with a first end thereof being integralwith and extending from the free edge or from the edge portion (7A, 8A;107A, 108A) of a respective side wall (7, 8; 107, 108) and with a secondfree end thereof forming a support lug (6B; 106B) intended for engagingthe inner surface of a wall (21, 22) of the chassis (20) and in that thelocking tabs adjacent said first end are provided with pawls (6C; 106C)intended for engaging the outer surface of a wall (21, 22) of thechassis (20), to thereby fix the guide and support structure to saidchassis wall.
 15. Guide and support structure (1; 100) according toclaim 14, characterized in that the locking tabs (6; 106) are providedwith two pawls (6C; 106C) being extended in mutually opposite directionsfrom side edges of the main portions (6A; 106A) of the locking tabs. 16.Guide and support structure (1; 100) according to any of claims 13-15,characterized in that the locking tabs (6; 106) are distributed at equaldistances from each other along each of the free edges or along each ofthe edge portions (7A, 8A; 107A, 108A) of the side walls (7, 8; 107,108) and in that the locking tabs of one side wall are displaced withhalf a pitch in relation to the locking tabs of the other side wall. 17.Guide and support structure (1; 100; 200) according to any of thepreceding claims, characterized in that the elongate profile ismanufactured from a stainless steel material that is tin plated.